Effect of sodium chloride and pH on the outgrowth of spores of type E Clostridium botulinum at optimal and suboptimal temperatures.
The sodium chloride inhibition of spore outgrowth of four strains of type E Clostridium bolulinum was determined in a Trypticase-peptone-glucose (TPG) medium. At 16, 21, and 30 C, spores of three strains required 5.0% and one strain 4.5% salt for complete inhibition during 1 year of incubation. At 8 and 10 C, spores of the four strains required 4.5% salt for definite inhibition. Salt concentrations slightly lower than those providing inhibition tended to extend spore outgrowth time at low temperatures. The minimal pH permitting outgrowth of type E spore inocula was affected by the concentration of reducing compound present in the system. When either 0.02% sodium thioglycolate or 0.05% L-cysteine hydrochloride was used, outgrowth at 30 and 8 C occurred at much lower pH levels than when 0.2% thioglycolate was added. At 30 C, spores of one strain showed outgrowth in TPG medium as low as pH 5.21 with an inoculum of 2 million spores per replicate tube. At a 10-fold higher inoculum, the same strain showed outgrowth at pH 5.03 in one of five replicate tubes. At 8 C, spore outgrowth of the four strains occurred at pH 5.9, but not at pH 5.7, in TPG medium containing L-cysteine hydrochloride.
D003014:Clostridium botulinum / Q000254:growth & development*; D003470:Culture Media; D006016:Glycolates / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D012965:Sodium Chloride / Q000494:pharmacology; D013170:Spores; D013696:Temperature
D003470:Culture Media; D006016:Glycolates; D012965:Sodium Chloride